Comment on The Major Role Of Land Cover/Land Use Change Within The Global Climate System – Another Ignored Issue in the 2007 IPCC Statement For Policymakers

In answer to a question from a reporter on the importance of land cover/land use change within the climate system, I wrote the response below, which briefly overviews why this climate forcing is so important. The lack of including an emphasis on this issue in the IPCC Statement for Policymakers is disappointing and shows their continued neglect of critically important issues in climate variability and change.

“The focus on a global average surface temperature obscures the actual impact of climate forcings on weather patterns. As shown, for example, in

Feddema et al. 2005: The importance of land-cover change in simulating future climates., 310, 1674-1678,

Pielke Sr., R.A., 2005: Land use and climate change. Science, 310, 1625-1626,

and

Marland, G., R.A. Pielke, Sr., M. Apps, R. Avissar, R.A. Betts, K.J. Davis, P.C. Frumhoff, S.T. Jackson, L. Joyce, P. Kauppi, J. Katzenberger, K.G. MacDicken, R. Neilson, J.O. Niles, D. dutta S. Niyogi, R.J. Norby, N. Pena, N. Sampson, and Y. Xue, 2003: The climatic impacts of land surface change and carbon management, and the implications for climate-change mitigation policy. Climate Policy, 3, 149-157.

land use/land cover change result in tropospheric warming in some regions, but cooling in others. The effect on a global average temperature is quite small (at least in the model studies performed so far), but the effect of changing the regional tropospheric heating/cooling patterns is a very significant effect on important weather events such as drought.

Thus the spatial heating change within the atmosphere due to land use/land cover change (and also from the diverse effect of anthropogenic aerosols) resuly in large changes in the the global weather patterns. This can occur irrespective of a global surface temperature trend.

For further information on this issue, see the 2002 NASA press release below is of interest:

LANDCOVER CHANGES MAY RIVAL GREENHOUSE GASES AS CAUSE OF CLIMATE CHANGE

See also the 2005 article in the NASA Earth Observatory

http://earthobservatory.nasa.gov/Study/DeepFreeze/ [last page]

where it is written,

“Local or Global Problem?

Though their results drew national media attention from many sources, all the scientists involved in the research agree that the scientific arena is where the results should be evaluated. Pielke hopes these results will convince scientists to give the land cover-climate connection more attention. In the past, he has been frustrated by the lack of attention to the topic.

Gordon Bonan is a climate modeler for the National Center for Atmospheric Research in Boulder, Colorado. ‘It’s definitely true that historically, the emphasis in global climate change research has been on other climate forcings—greenhouses gases, solar variability, aerosols—and that the role of land cover has been neglected. Roger’s work, his persistence, has really played a large role in bringing people around to the importance of it.’ Bonan thinks people are finally beginning to listen.

So far, what research has been done on the global-scale influence of land cover change on climate seems to suggest it plays a minor role. That’s not surprising, says Bonan, considering how small the Earth’s land surface is compared to its oceans and that our most common metric for climate change is global mean temperature. Even significant changes in the temperature where we live can get ‘washed out’ (at least for a while) in the global average of a world mostly covered by oceans.

‘Nobody experiences the effect of a half a degree increase in global mean temperature,’ Bonan says. ‘What we experience are the changes in the climate in the place where we live, and those changes might be large. Land cover change is as big an influence on regional and local climate and weather as doubled atmospheric carbon dioxide—perhaps even bigger.’ That’s the idea Pielke says he has been trying to get across for years. ‘Climate change is about more than a change in global temperature,’ he says. ‘It’s about changes in weather patterns across the Earth.’ Even if it turns out that land cover change doesn’t significantly alter the globally-averaged surface temperature of the Earth, it’s still critically important. ‘The land is where we live. This research shows that the land itself exerts a first order [primary] influence on the climate we experience.’

If land cover change can cause Florida to have hotter, drier summers and chillier, longer-lasting cold spells, then that is a perfect example of why, Pielke says, ‘we can’t keep looking solely at increasing carbon dioxide as the only important forcing of climate by people.'”

By neglecting the important role of land cover/land use change within the global climate system, as documented in the peer reviewed literature, the IPCC has again shown its bias and narrow perspective as an advocacy document to promote energy policy changes, but not climate policy.

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